Transparent box background artifcats with two lines subtitle

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Transparent box background artifcats with two lines subtitle

Unread postby sup » Sat Feb 18, 2017 12:20 pm

If you want to set your subtitles onto a box that is not opaque but semi-transparent, you can easily do it with aegisub as per here: http://stackoverflow.com/questions/2587 ... 2_25880038

However, if the subtitles contain more then one line, there is an ugly artifact. In the link above, they say it is a bug in libass. However, the aegisub bug tracker is down now, where could I report it? Is it likely to get fixed? (I looked at aegisub github account and there do not seem to be a lot of commits lately)
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Re: Transparent box background artifcats with two lines subt

Unread postby jfs » Sat Feb 18, 2017 2:09 pm

It's a bug in the "specification". The format was effectively specified to work that way some 12-15 years ago, and changing it would potentially make someone's subtitles stop looking right.

The workaround is to manually create a box or other shape with the drawing commands, and make sure it's layered below the subtitles. This can be automated, although I'm not sure if anything for it exists already.
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Re: Transparent box background artifcats with two lines subt

Unread postby sup » Sat Feb 18, 2017 4:58 pm

I know that I can draw a box, but I would like the box to be displayed only when subtitles are displayed. I guess I could script something that would draw the box only when the subtitles are displayed (and that would also be only as big as the subtitles are) but that is a bit complicated (I use VLC for this but that is not very flexible nor fast).

Could not the specification of the format be updated with a new Borderstyle? If I look correctly, "3" means a box. So, for example, "5" could mean "box without tha artifact". That would be backwards compatible, woudln't it?
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Re: Transparent box background artifcats with two lines subt

Unread postby jfs » Sat Feb 18, 2017 5:32 pm

Well yes you could add a new border style that would be "like 3 but more sensible", then you'd just have people with old renderers getting no borders at all. I think.

Either way, it's not really something that starts with Aegisub. Your best bets for getting in contact with current developers that touch VSFilter and libass would be the MPC-HC, VLC, and mpv projects.
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Re: Transparent box background artifcats with two lines subt

Unread postby sup » Sun Feb 19, 2017 2:02 pm

Ok, thanks, I filed a bug here: https://github.com/libass/libass/issues/268

It is a pity ASS v. 5.0 is not happening as it seems:-(
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Re: Transparent box background artifcats with two lines subt

Unread postby sup » Sun Feb 19, 2017 2:19 pm

Turns out setting BorderStyle=4 actually accomplishes what I want when using libass!
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